In a related art, as a method of auto focus in an imaging apparatus such as a digital single-lens reflex camera, a contrast detection scheme is commonly used widely. In the contrast detection scheme, on the basis of an image signal that is captured by an imaging element, a contrast value of an image signal in an area that is specified by an auto focus window (specification range) is extracted as a focus evaluation value. In addition, a lens position at which a contrast value that is the focus evaluation value becomes large is detected as a focus position.
In addition, as another scheme of auto focus, there is a high frequency component detection scheme. In the high frequency component detection scheme, a high frequency component of the image signal in the specification range is extracted as the focus evaluation value, and a lens position at which a value of the high frequency component becomes large is detected as the focus position. The performance of the auto focus in high frequency component detection scheme is higher than the performance of the auto focus in the contrast detection scheme.
The method of the focus is discussed, for example, in Japanese Unexamined Patent Application Publication No. H3-001668, and Japanese Examined Patent Publication No. H7-118785.